Fasteners for securing two panels or the like together can include a screw and a grommet. The grommet is inserted and retained within an aperture in a base or supporting panel and the shank of the screw is inserted through an aperture in a mating panel and then threadingly engaged within the grommet to secure the two panels together.
In order to retain the grommet within the aperture of the base panel, the base panel typically is captured between a head of the grommet and a shoulder formed on the body of the grommet. Upon insertion of the grommet into the aperture, the shoulders extend through the panel aperture and engage a back side of the panel thereby retaining the grommet thereto.
Existing screw and grommet fasteners typically are designed so that the grommet is relatively inflexible and only can accept a screw of a particular size and having dimensions which fall within a narrow range. Accordingly, if an attempt is made to thread a screw into the grommet having the wrong size or dimensions outside the prescribed range, the screw either will not thread or the insertion torque will force the screw into the grommet and possibly cause the grommet to break.
Screws and grommets can both be formed from metal, plastic or a combination of a metal screw and a plastic grommet, or vice versa. Existing metal grommets typically can withstand screw insertion torques between 25-40 in./lbs. while existing plastic grommets typically only can withstand screw insertion torques between 5-10 in./lbs.
Additionally, during use, variations in the relative positions of the supporting panel and the mating panel occur which are caused by thermal expansion and contraction from changes in temperature. Such variations can cause one or both panels to become disfigured and possibly cause the fastener to fail.
In order to allow for such variations, oblong grommets typically are utilized which allow for expansion and contraction along a line. Such grommets, however, typically do not have much flexibility thereby causing the threads to strip from mis-sized screws under substantially low torque as described above. This particularly is true with a completely inflexible portion of the grommet positioned within the confines of the panel aperture between the head and the shoulder which prevents any expansion of the grommet and frequently will not accept the screw.
It therefore would be desirable to provide a screw and grommet fastener assembly for securing two mating panels together where the grommet allows for variations in the relative positions of the panels and flexing of the grommet body portion during insertion of the screw to accept screws of different sizes and slightly out of dimension and enable higher torques to be applied to the screw without causing damage to the grommet.